The first thing I would do is explain to the homeowner the Agent is going to expect his commission when the homeowner does the CA with you. If he's cool with that, then so be it. It's between homeowner and Agent and has no bearing on you. If a light bulb goes on and the homeowner realizes the folly of paying the Agent for not getting the job done, then perhaps he'll cancel his listing agreement. But again, that's between homeowner and Agent. Bottom line: if the homeowner gives you the go ahead, then do your thing, Erik.

In the future consider throwing a few bucks to the agent an make them sort of happy. If the agents deal is to rent,the the total commission is usually the first months rent and usually is split with an agent that brings in the renter. So what I am getting usually enough where this amounts to nothing and I can usually turn this agent into a sort of bird-dog or scout instead of a foe.

It'll always be easier to include the realtor. Because, if the realtor thinks you interfered with his contract he could sue you. Sometimes is better to make friends and make enemies. Just my opinion. And, the agent could help you show houses in the future. Which leaves you with more time to make more offers.